/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.function.server;

import java.net.InetSocketAddress;
import java.net.URI;
import java.nio.charset.Charset;
import java.security.Principal;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Optional;
import java.util.OptionalLong;
import java.util.function.Consumer;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import org.springframework.core.ParameterizedTypeReference;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.http.HttpCookie;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpRange;
import org.springframework.http.MediaType;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.json.Jackson2CodecSupport;
import org.springframework.http.codec.multipart.Part;
import org.springframework.http.server.PathContainer;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.BodyExtractor;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebSession;
import org.springframework.web.util.UriBuilder;

/**
 * Represents a server-side HTTP request, as handled by a {@code HandlerFunction}.
 *
 * <p>Access to headers and body is offered by {@link Headers} and
 * {@link #body(BodyExtractor)}, respectively.
 *
 * @author Arjen Poutsma
 * @author Sebastien Deleuze
 * @since 5.0
 */
public interface ServerRequest {

    /**
     * Get the HTTP method.
     *
     * @return the HTTP method as an HttpMethod enum value, or {@code null}
     * if not resolvable (e.g. in case of a non-standard HTTP method)
     */
    @Nullable
    default HttpMethod method() {
        return HttpMethod.resolve(methodName());
    }

    /**
     * Get the name of the HTTP method.
     *
     * @return the HTTP method as a String
     */
    String methodName();

    /**
     * Get the request URI.
     */
    URI uri();

    /**
     * Get a {@code UriBuilderComponents} from the URI associated with this
     * {@code ServerRequest}.
     * <p><strong>Note:</strong> as of 5.1 this method ignores {@code "Forwarded"}
     * and {@code "X-Forwarded-*"} headers that specify the
     * client-originated address. Consider using the {@code ForwardedHeaderFilter}
     * to extract and use, or to discard such headers.
     *
     * @return a URI builder
     */
    UriBuilder uriBuilder();

    /**
     * Get the request path.
     */
    default String path() {
        return uri().getRawPath();
    }

    /**
     * Get the request path as a {@code PathContainer}.
     */
    default PathContainer pathContainer() {
        return PathContainer.parsePath(path());
    }

    /**
     * Get the headers of this request.
     */
    Headers headers();

    /**
     * Get the cookies of this request.
     */
    MultiValueMap<String, HttpCookie> cookies();

    /**
     * Get the remote address to which this request is connected, if available.
     *
     * @since 5.1
     */
    Optional<InetSocketAddress> remoteAddress();

    /**
     * Get the readers used to convert the body of this request.
     *
     * @since 5.1
     */
    List<HttpMessageReader<?>> messageReaders();

    /**
     * Extract the body with the given {@code BodyExtractor}.
     *
     * @param extractor the {@code BodyExtractor} that reads from the request
     * @param <T>       the type of the body returned
     * @return the extracted body
     * @see #body(BodyExtractor, Map)
     */
    <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor);

    /**
     * Extract the body with the given {@code BodyExtractor} and hints.
     *
     * @param extractor the {@code BodyExtractor} that reads from the request
     * @param hints     the map of hints like {@link Jackson2CodecSupport#JSON_VIEW_HINT}
     *                  to use to customize body extraction
     * @param <T>       the type of the body returned
     * @return the extracted body
     */
    <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor, Map<String, Object> hints);

    /**
     * Extract the body to a {@code Mono}.
     *
     * @param elementClass the class of element in the {@code Mono}
     * @param <T>          the element type
     * @return the body as a mono
     */
    <T> Mono<T> bodyToMono(Class<? extends T> elementClass);

    /**
     * Extract the body to a {@code Mono}.
     *
     * @param typeReference a type reference describing the expected response request type
     * @param <T>           the element type
     * @return a mono containing the body of the given type {@code T}
     */
    <T> Mono<T> bodyToMono(ParameterizedTypeReference<T> typeReference);

    /**
     * Extract the body to a {@code Flux}.
     *
     * @param elementClass the class of element in the {@code Flux}
     * @param <T>          the element type
     * @return the body as a flux
     */
    <T> Flux<T> bodyToFlux(Class<? extends T> elementClass);

    /**
     * Extract the body to a {@code Flux}.
     *
     * @param typeReference a type reference describing the expected request body type
     * @param <T>           the element type
     * @return a flux containing the body of the given type {@code T}
     */
    <T> Flux<T> bodyToFlux(ParameterizedTypeReference<T> typeReference);

    /**
     * Get the request attribute value if present.
     *
     * @param name the attribute name
     * @return the attribute value
     */
    default Optional<Object> attribute(String name) {
        Map<String, Object> attributes = attributes();
        if (attributes.containsKey(name)) {
            return Optional.of(attributes.get(name));
        } else {
            return Optional.empty();
        }
    }

    /**
     * Get a mutable map of request attributes.
     *
     * @return the request attributes
     */
    Map<String, Object> attributes();

    /**
     * Get the first query parameter with the given name, if present.
     *
     * @param name the parameter name
     * @return the parameter value
     */
    default Optional<String> queryParam(String name) {
        List<String> queryParamValues = queryParams().get(name);
        if (CollectionUtils.isEmpty(queryParamValues)) {
            return Optional.empty();
        } else {
            String value = queryParamValues.get(0);
            if (value == null) {
                value = "";
            }
            return Optional.of(value);
        }
    }

    /**
     * Get all query parameters for this request.
     */
    MultiValueMap<String, String> queryParams();

    /**
     * Get the path variable with the given name, if present.
     *
     * @param name the variable name
     * @return the variable value
     * @throws IllegalArgumentException if there is no path variable with the given name
     */
    default String pathVariable(String name) {
        Map<String, String> pathVariables = pathVariables();
        if (pathVariables.containsKey(name)) {
            return pathVariables().get(name);
        } else {
            throw new IllegalArgumentException("No path variable with name \"" + name + "\" available");
        }
    }

    /**
     * Get all path variables for this request.
     */
    Map<String, String> pathVariables();

    /**
     * Get the web session for this request.
     * <p>Always guaranteed to return an instance either matching the session id
     * requested by the client, or with a new session id either because the client
     * did not specify one or because the underlying session had expired.
     * <p>Use of this method does not automatically create a session.
     */
    Mono<WebSession> session();

    /**
     * Get the authenticated user for the request, if any.
     */
    Mono<? extends Principal> principal();

    /**
     * Get the form data from the body of the request if the Content-Type is
     * {@code "application/x-www-form-urlencoded"} or an empty map otherwise.
     * <p><strong>Note:</strong> calling this method causes the request body to
     * be read and parsed in full, and the resulting {@code MultiValueMap} is
     * cached so that this method is safe to call more than once.
     */
    Mono<MultiValueMap<String, String>> formData();

    /**
     * Get the parts of a multipart request if the Content-Type is
     * {@code "multipart/form-data"} or an empty map otherwise.
     * <p><strong>Note:</strong> calling this method causes the request body to
     * be read and parsed in full, and the resulting {@code MultiValueMap} is
     * cached so that this method is safe to call more than once.
     */
    Mono<MultiValueMap<String, Part>> multipartData();

    /**
     * Get the web exchange that this request is based on.
     * <p>Note: Manipulating the exchange directly (instead of using the methods provided on
     * {@code ServerRequest} and {@code ServerResponse}) can lead to irregular results.
     *
     * @since 5.1
     */
    ServerWebExchange exchange();


    // Static builder methods

    /**
     * Create a new {@code ServerRequest} based on the given {@code ServerWebExchange} and
     * message readers.
     *
     * @param exchange       the exchange
     * @param messageReaders the message readers
     * @return the created {@code ServerRequest}
     */
    static ServerRequest create(ServerWebExchange exchange, List<HttpMessageReader<?>> messageReaders) {
        return new DefaultServerRequest(exchange, messageReaders);
    }

    /**
     * Create a builder with the status, headers, and cookies of the given request.
     *
     * @param other the response to copy the status, headers, and cookies from
     * @return the created builder
     * @since 5.1
     */
    static Builder from(ServerRequest other) {
        return new DefaultServerRequestBuilder(other);
    }


    /**
     * Represents the headers of the HTTP request.
     *
     * @see ServerRequest#headers()
     */
    interface Headers {

        /**
         * Get the list of acceptable media types, as specified by the {@code Accept}
         * header.
         * <p>Returns an empty list if the acceptable media types are unspecified.
         */
        List<MediaType> accept();

        /**
         * Get the list of acceptable charsets, as specified by the
         * {@code Accept-Charset} header.
         */
        List<Charset> acceptCharset();

        /**
         * Get the list of acceptable languages, as specified by the
         * {@code Accept-Language} header.
         */
        List<Locale.LanguageRange> acceptLanguage();

        /**
         * Get the length of the body in bytes, as specified by the
         * {@code Content-Length} header.
         */
        OptionalLong contentLength();

        /**
         * Get the media type of the body, as specified by the
         * {@code Content-Type} header.
         */
        Optional<MediaType> contentType();

        /**
         * Get the value of the required {@code Host} header.
         * <p>If the header value does not contain a port, the
         * {@linkplain InetSocketAddress#getPort() port} in the returned address will
         * be {@code 0}.
         */
        @Nullable
        InetSocketAddress host();

        /**
         * Get the value of the {@code Range} header.
         * <p>Returns an empty list when the range is unknown.
         */
        List<HttpRange> range();

        /**
         * Get the header value(s), if any, for the header of the given name.
         * <p>Returns an empty list if no header values are found.
         *
         * @param headerName the header name
         */
        List<String> header(String headerName);

        /**
         * Get the headers as an instance of {@link HttpHeaders}.
         */
        HttpHeaders asHttpHeaders();
    }


    /**
     * Defines a builder for a request.
     *
     * @since 5.1
     */
    interface Builder {

        /**
         * Set the method of the request.
         *
         * @param method the new method
         * @return this builder
         */
        Builder method(HttpMethod method);

        /**
         * Set the URI of the request.
         *
         * @param uri the new URI
         * @return this builder
         */
        Builder uri(URI uri);

        /**
         * Add the given header value(s) under the given name.
         *
         * @param headerName   the header name
         * @param headerValues the header value(s)
         * @return this builder
         * @see HttpHeaders#add(String, String)
         */
        Builder header(String headerName, String... headerValues);

        /**
         * Manipulate this request's headers with the given consumer.
         * <p>The headers provided to the consumer are "live", so that the consumer can be used to
         * {@linkplain HttpHeaders#set(String, String) overwrite} existing header values,
         * {@linkplain HttpHeaders#remove(Object) remove} values, or use any of the other
         * {@link HttpHeaders} methods.
         *
         * @param headersConsumer a function that consumes the {@code HttpHeaders}
         * @return this builder
         */
        Builder headers(Consumer<HttpHeaders> headersConsumer);

        /**
         * Add a cookie with the given name and value(s).
         *
         * @param name   the cookie name
         * @param values the cookie value(s)
         * @return this builder
         */
        Builder cookie(String name, String... values);

        /**
         * Manipulate this request's cookies with the given consumer.
         * <p>The map provided to the consumer is "live", so that the consumer can be used to
         * {@linkplain MultiValueMap#set(Object, Object) overwrite} existing cookies,
         * {@linkplain MultiValueMap#remove(Object) remove} cookies, or use any of the other
         * {@link MultiValueMap} methods.
         *
         * @param cookiesConsumer a function that consumes the cookies map
         * @return this builder
         */
        Builder cookies(Consumer<MultiValueMap<String, HttpCookie>> cookiesConsumer);

        /**
         * Set the body of the request.
         * <p>Calling this methods will
         * {@linkplain org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer) release}
         * the existing body of the builder.
         *
         * @param body the new body
         * @return this builder
         */
        Builder body(Flux<DataBuffer> body);

        /**
         * Set the body of the request to the UTF-8 encoded bytes of the given string.
         * <p>Calling this methods will
         * {@linkplain org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer) release}
         * the existing body of the builder.
         *
         * @param body the new body
         * @return this builder
         */
        Builder body(String body);

        /**
         * Add an attribute with the given name and value.
         *
         * @param name  the attribute name
         * @param value the attribute value
         * @return this builder
         */
        Builder attribute(String name, Object value);

        /**
         * Manipulate this request's attributes with the given consumer.
         * <p>The map provided to the consumer is "live", so that the consumer can be used
         * to {@linkplain Map#put(Object, Object) overwrite} existing attributes,
         * {@linkplain Map#remove(Object) remove} attributes, or use any of the other
         * {@link Map} methods.
         *
         * @param attributesConsumer a function that consumes the attributes map
         * @return this builder
         */
        Builder attributes(Consumer<Map<String, Object>> attributesConsumer);

        /**
         * Build the request.
         *
         * @return the built request
         */
        ServerRequest build();
    }

}
